Size reduction machines utilise a frusto-conical shaped screen located in a channel between an input and an output. Such size reduction machines are more particularly described in U.S. Pat. Nos. 4,759,507 and 5,330,113. In these machines, various screens and impellers are used depending on the size and type of product that is being processed. The screens have apertures in different sizes and shapes to produce a desired milled product.
The production of cosmetics presents particular problems. The particulate size of cosmetics is required to be very fine. As a result fine screens with fine mesh sizes are needed. These screens are delicate and are often damaged during use and during cleaning, requiring frequent replacement.
A secondary screen has been used as support for the primary fine screen in addressing the problem of breakage during use. However, the primary screen is still able to be separated from the secondary screen. Since cosmetics production requires frequent cleaning, the fine screens are routinely damaged once the fine screen has become separated from the secondary screen during cleaning.